A Billerica priest has resigned after allowing a church volunteer - a former priest accused of sexually abusing a girl in the 1970s - chaperone teenagers on a trip to upstate New York last year, according to a statement by the Archdiocese of Boston and court documents.

The Rev. Eugene Tully will be reassigned to a new parish after ministering at the St. Theresa of Lisieux Parish in Billerica for 19 years, according to the archdiocese, which delivered a message announcing the move during Mass this weekend.

Tully "exercised a serious error in judgment" when he allowed Renald C. Hallee, a longtime congregant and youth minister, to chaperone the teens, the archdiocese statement said.

According to documents filed with the Maine Supreme Judicial Court, Hallee was notified in early April of a civil lawsuit filed against him in Portland, Maine, in March.

He was alerted to the suit 17 days before he was to accompany the Saint Theresa teens to a farm in upstate New York for a weeklong service project.

Soon after learning of the suit, Hallee told Tully.

"Once [Tully] had the knowledge of the civil suit, he shouldn't have allowed the volunteer to go on the trip," Terrence Donilon, spokesman for the Archdiocese, said in a phone interview.

Since Tully's resignation, effective last Friday, Hallee has withdrawn from youth ministering activities, said Phil DiBello, a church deacon.

Tully, who is nearly 70, has spent more than 40 years in the priesthood.

There were no accusations of misconduct during the service project, and Hallee had recently passed an annual mandatory criminal background check, Donilon said.

The charges against Hallee date from 1970 to 1973, when he was a priest at St. John's Parish in Bangor, where he allegedly assaulted an 8-year-old girl, according to court records.

Hallee left Maine - and the priesthood - around 1977, Keith Varner, a lawyer for the alleged victim, said yesterday.

Russell B. Pierce Jr., a lawyer for Hallee, said that his client denies the allegations in the Maine lawsuit.

The case against Hallee is pending in Maine's highest appeals court, which must decide if statute of limitation rules apply to the victim.

The court's final word could come at any time, Varner said.

At St. Theresa, the weekend has brought upheaval, parishioners said.

The parish regularly counts 1,500 at weekend Mass, according to the archdiocese.

DiBello, 52, a longtime friend of Hallee, said he and others are shocked by the serious charges leveled against a member of the church community.

DiBello said that Hallee told him in a private conversation that he used to be a priest, but never mentioned allegations of sexual misconduct when he talked about why he left.

"He's a deeply, deeply spiritual man with deep roots in Scripture," DiBello said of Hallee.